Low reflectance optical web

ABSTRACT

An optical web comprising includes a substrate with an anterior coating applied to the anterior side of the substrate and a posterior coating applied to the posterior side of the substrate. The refractive index of the anterior coating and the posterior coating is less than that of the substrate. A second coating layer may be applied to the anterior coating layer and/or the posterior coating layer, where the second coating layer has a refractive index less than that of the coating layer it is applied to. Additional coating layers may be applied to produce a stack of layers that decrease monotonically in refractive indexes moving outward from the substrate. The optical webs may be laminated together to form tear-off laminated lens stacks.

RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.16/545,021, filed Aug. 20, 2019, now U.S. Pat. No. 11,141,959 B2, issuedOct. 12, 2021, which is a continuation of prior application Ser. No.15/663,062, filed Jul. 28, 2017, now U.S. Pat. No. 10,427,385 B2, issuedOct. 1, 2019, which claims the priority benefit of U.S. ProvisionalPatent Application No. 62/367,845, filed Jul. 28, 2016, which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

This application generally relates to optical webs. More specifically,the present disclosure relates to optical webs coated with non-thin filmcoatings to reduce reflectance.

BACKGROUND

Optical windows can be used to protect the face and eyes of a wearerfrom spatter, debris, and other projectiles that can cause harm to awearer's face and eyes while still allowing the wearer to see clearlythrough the window. For example, helmets, face masks, goggles,windshields and the like are used in a variety of differentenvironments, such as in racing (e.g., horse, auto, motorcycle, bike,etc.), workshops and laboratories, and surgical environments, to namebut a few. In many of these environments, spatter and other debris canaccrue on the eyewear, thereby occluding the field of vision for a user.Moreover, in addition to the issues caused by a soiled window, glarecaused by the reflections of light off the window can also inhibit thewearer's ability to see clearly. In many of these environments, suchvisual imparities can present serious health and safety issues. Forinstance, in environments that involve high speed travel (e.g., racing),or complicated technical endeavors (medical procedures), visualobstructions caused by spatter or glare can have a negative impact onperformance and result in untimely accidents or errors that can poseserious risks.

Regarding visibility issues caused by spatter and debris, it is notalways possible or effective to simply wipe away the spatter to clearthe field of vision. For instance, racers and surgeons frequently willnot have a free hand or a towel available to wipe their eyewear clean,and even if they did, such wiping could still smear or leave behindresidue that could occlude the field of vision. One technique forhelping such individuals clear their field of vision involves providingtear-off lenses on the eye protector. In this way, wearers can remove anouter-most tear-off lens layer when it becomes soiled, thereby exposinga clean layer underneath to provide a clear field of vision. Moretear-off lenses on the eyewear provide more opportunities for the wearerto clear their field of vision; however, each layer in a tear-off lensstack can further contribute to the glare generated.

Glare and reflectance off an optical surface can be reduced by employinganti-reflective coating (AR coating) on the optical surface. AR coatingstypically consist of many transparent thin film structures that havealternating layers of contrasting refractive index. In this sense, “thinfilms” is not a relative term, but instead refers to films that have athickness that is on the order of half the wavelength of visible light,or less. For instance, thin films may refer to films having a thicknessof between 50 nm to 250 nm (0.05 microns to 0.25 microns) or eventhinner. The thin film layers are chosen to make up the AR coating areselected to produce destructive interference in the beams reflected fromthe surfaces and constructive interference in the correspondingtransmitted beams. While these AR coatings can be effective in reducingreflections, they are also expensive to produce and apply. For example,the thin film AR coatings are typically applied either in a vacuumenvironment or by spin coating. However, vacuum environments forprocessing are very expensive and preclude commercial use of large areadisposable lenses. And spin coating is suitable for application onsmall, round substrates having an area less than one square foot, but isnot viable for web processing. In addition, thin film AR coatings aresubject to color shift, such that when viewed at angles, the AR coatingstend to provide a colored hue or tint (e.g., a violet hue), which mayundesirably take away from viewing in environments where clear vision isparamount. Accordingly, using AR coatings to reduce glare on opticalwebs or products formed therefrom, on laminated material such astear-off lens stacks, or on other disposable materials such asdisposable shields and windows, is not a cost effective technique forreducing reflections.

SUMMARY

This application describes examples of optical webs and related methodsof manufacture and use. The optical webs comprise one or more layersthat can be applied to or used as a protective eyewear or otherprotective optical structure, such as goggles, a face shield, a mask, ahelmet, glasses, a window, a windshield, or the like. The optical websare designed to reduce, limit, minimize, or otherwise reduce the glareor reflections off and through the webs.

Generally speaking, the optical webs include a substrate layer and acoating stack applied to one or both sides of the substrate. The coatingstacks may include one or more optical coating layers. The substrate hasa refractive index that, by itself, would reflect a certain amount oflight resulting in glare when viewed. The coating stacks are arrangedwith optical coating layers that have a lower refractive index than thatof the substrate. The coatings are arranged so that no air or othersurfaces are applied between the various layers. Where the coating stackincludes multiple coating layers, the refractive indexes of each of theoptical coating layers are selected so that the refractive indexesdecrease monotonically from the substrate to the outer surface (i.e.,the refractive index decreases from layer to layer moving from thesubstrate outward, without increasing). Thus, each outwardly successiveoptical coating layer has a lower refractive index than that of thecoating layer it is applied to. In this way, the outermost coating layerhas the lowest refractive index of the coating stack. This monotonicdecreasing refractive index helps reduce the glare generated by theoptical web. That is, the glare generated by the optical web is lowerthan the glare that would result from the substrate by itself. The webcan be provided as a sheet or roll, or it may be cut to shape, forexample, to the shape of a window, screen, shield, or other structure.

In some examples, the optical webs are used to form multi-layerlaminated material. The multi-layer material can include two or morelayers of the optical webs described above laminated together with apeelable adhesive so that the layers can be released from the stack. Inthis way, the multi-layer material can be cut into multi-layer stacks,which can then be used as a multi-layer window, or applied thereto. Inoperation, when desired (e.g., when it becomes soiled), the outermostlayer of the stack can be peeled or torn away to reveal a cleansubsequent layer, thereby providing a clear field of vision. In someexamples, the stack includes multiple layers that are all of the same asone another (e.g., multiple layers of the optical webs described abovelaminated to one another), but in other examples the layers of the stackcan be different. For example, the stack may include a base layer thathas a thickness greater than that of the other layers, thereby providingrigidity to the stack so that the stack can be used as a window orshield. The multi-layer laminated material can be provided as a sheet orroll of material, or it can be cut to a shape, for example, the shape ofa shield or window. In some instances, the shield can be sterilized(e.g., using gamma sterilization) and coupled to a garment, such as amedical garment, where it can be used in a sterile medical environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an optical web in accordance withexamples described in this application.

FIG. 2 is a side elevation view of the optical web of FIG. 1 .

FIG. 3 is a side elevation view of an optical web coated with a coatingstack in accordance with examples described herein.

FIG. 4 is a side elevation view of an optical web coated with coatingstacks on anterior and posterior sides in accordance with examplesdescribed herein.

FIG. 5 is a side elevation view of an optical web comprising a stack oflaminated optical layers in accordance with examples described herein.

FIG. 6A shows a roll of optical web material in accordance with examplesdescribed herein.

FIG. 6B shows the optical web material of FIG. 6A being converted intooptical windows.

FIG. 6C shows the optical windows of FIG. 6B being attached to agarment.

FIG. 7A is a diagram depicting a method for manufacturing an optical webin accordance with examples described in this application.

FIG. 7B is a diagram depicting another method for manufacturing anoptical web in accordance with examples described herein.

FIGS. 8A and 8B are diagrams demonstrating the effect of the reflectanceof light for an uncoated substrate and an optical web material coatedwith multiple coating stacks.

DETAILED DESCRIPTION

This application describes examples of optical webs and related methodsof manufacture and use. The optical webs comprise multiple layers,including a base substrate, and at least one coating layer. Therefractive indexes of the various layers decrease monotonically from thesubstrate outward, at least in one direction. That is, the coating layerapplied directly to the substrate will have a lower refractive indexthan the substrate, and any coating layer applied thereto will have yetan even lower refractive index, as will each successive coating layer.The coatings and coating stacks can be applied to one or both sides of asubstrate. This configuration allows for an optical web to reducereflections and glare over the substrate material by itself withoutrelying on expensive and difficult to apply thin film coatings.

The described optical webs can be made without employing expensive andfragile thin films or AR coatings. That is, the coating layers andsubstrate can be made at thicknesses that are less expensive to produceand assemble than the thin films forming AR coatings. In general, thecoating layers applied to the substrate can be at least four timesthicker wavelength of visible light. In some cases, the coating layerscan be at least 2 microns thick (i.e., 2 micrometers or 2000 nm thick);however, depending on the intended application and use and tolerance forcost, the coatings can be even thinner, for example 0.5 microns. Ingeneral, the described coating layers can achieve glare reduction usingprinciples of refraction and Snell's law without addressing or dealingwith thin film interference issues.

While the described optical webs can be made without using thin filmcoatings, certain examples may still apply such thin film AR coatings tothe webs. For instance, some webs may include an AR coating applieddirectly to a substrate surface opposite the other coated surfaces, andin other cases, webs may include an AR coating on top of an outermostcoating layer to provide additional anti-glare benefits. For instance,this application claims priority to, and incorporates by reference U.S.provisional patent application No. 62/367,845, titled “ScreenProtector,” which describes applying an AR coating applied to anunderside or interior surface of a web product that is used as a screenprotector. Examples of such a screen protector are further describedbelow.

Snell's law (also known as the law of refraction) presents formulas thatdescribe the relationship between the angles of incidence andrefraction, when referring to light or other waves passing through aboundary between two different isotropic media, such as water, air,glass, polymers, or other substances. In optics, the law is used tocompute the angles of incidence or refraction, and in experimentaloptics to find the refractive index of a material. The refractive indexof a medium is a representation of how light propagates through themedium, and is represented by the equation:n=c/vwhere n is the refractive index of the medium, c is the speed of lightin a vacuum, and v is the phase velocity of the light medium. Generally,a higher refractive index means that light travels slower through themedium.

Snell's law states that the ratio of the sines of the angles ofincidence and refraction is equivalent to the ratio of phase velocitiesin the two media, or equivalent to the reciprocal of the ratio of theindices of refraction. At an interface between two different media(e.g., a substrate and air, a substrate and a coating, a film and anadhesive, etc.) the interface will reflect a percentage of light, andthat percentage depends upon the difference between the refractiveindexes of the two media and the angles of incidence and refraction. Ingeneral, the larger the difference between the refractive indexes of twomedia forming the interface, the more light the interface will reflect.For the case of normal incidence, where the angle of incidence andrefraction are both zero, reflectance can be measured by squaring thequotient of the difference between the refractive indexes of the twomaterials and their sums. In other words, reflectance can be representedby the following equation:

$R = {\frac{n_{1} - n_{2}}{n_{1} + n_{2}}}^{2}$Where R is the reflectance, and n₁ and n₂ are the respective refractiveindexes of the two materials forming the interface.

Typically, the index of refraction of air is about 1 (more specifically,it is about 1.0003). Because air is a medium through which lighttravels, the surface of any optical substance creates an interface thatwill reflect and refract light. And for materials used as a window, thematerial will form two interfaces with air—on the anterior and posteriorside of the medium—thereby contributing to reflectance and glare twice.Table 1 applies the normal incidence equation above to demonstrate thepercentage of light that will be reflected by a material having aparticular refractive index (RI) when viewed through air.

TABLE 1 RI of Reflectance % Total Reflectance Material RI of Air FromOne Surface From Two Surfaces 1.00 1.00 0  0.000% 1.30 1.00 1.701% 3.403% 1.35 1.00 2.218%  4.436% 1.40 1.00 2.778%  5.556% 1.45 1.003.374%  6.747% 1.50 1.00 4.000%  8.000% 1.55 1.00 4.652%  9.304% 1.601.00 5.325% 10.651% 1.65 1.00 6.016% 12.033% 1.70 1.00 6.722% 13.443%

As shown in Table 1, not only do greater differences in refractive indexproduce greater reflectance, the increase in reflectance is not linear.That is, a difference in refractive index of 0.3 results in a totalreflectance of 3.4%, but doubling that difference to 0.6 results in atotal reflectance of 10.65%, which is more than three times thereflectance.

In certain circumstances, it may be necessary to use materials withhigher refractive indexes for window type applications. For example,some equipment used in a medical environment, particular forenvironments related to surgical procedures, must be sterilized, andkept sterile prior to use. One technique for sterilizing equipmentinvolves exposing the product is exposed to gamma radiation. Such atechnique can be particularly useful, for example, for the sterilizationof equipment that includes multi-layer laminated lens stacks because thegamma radiation can penetrate the layers and sterilize the surfaces ofthe intermediary lenses of the stack. However, gamma radiation tends tocause certain materials to change in color or transparency. For example,gamma radiation tends to cause certain polymers, such as polycarbonateand poly methyl methacrylate (PMMA) to turn yellow, thereby making theproduct unsuitable, or at least less desirable, for use in certainmedical applications. Materials like polyester (e.g., BoPet) may be ableto withstand the gamma radiation treatment without discoloration, butthese materials tend to have a higher refractive index and thus resultin shields/windows that reflect more light and generate more glare. Thisincreased glare can be a particular problem in environments where asurgeon or other caregiver wears a headlamp or light source under theshield to illuminate work areas, which is often done to maintain asterile work environment. This increased glare can cause visibilityissues for the caregiver that can lead to potential serious health andsafety risks.

This application discloses a technique for reducing glare on opticalwebs and related products that can be used without using AR or otherthin film coatings. The described applications reduce reflections bylayering non-thin film coatings onto a substrate such that the coatingshave lower refractive indexes than the substrate. Where more than onecoating layer is used, the coatings are applied so that the refractiveindexes decrease monotonically from the substrate toward the web-airinterface. While the addition of coating layers may increase the numberof interfaces that will generate reflections, smaller differencesbetween the refractive indexes will result in less light being reflectedat each interface. Because larger refractive indexes have a greatereffect on reflectance, the monotonic layered configuration results in areduction in light reflectance.

As noted, this application describes examples of optical webs andproducts made from optical webs. In this sense, webs refer to a long,thin, and flexible material. Webs can be continuous sheets, and a singleweb can have a significantly large surface area, particularly withrespect to other optical components such as camera lenses, eyeglasses,and the like. The described optical webs and can be provided on a sheetor on a roll material, and can be subsequently converted into variousoptical products, such as lenses, windows, shields, covers, or the like.Alternatively, the described optical webs can refer to optical productsthat have already been cut or formed to shape. For example, the opticalwebs described herein can refer to a roll of web material, a sheet ofweb material, a face shield or windshield cut or shaped from webmaterial, or the like.

The term “optical webs” as described herein may refer to a single weblayer (not including coatings as a “layer” in this sense). The term mayalso refer to stacks formed from multiple optical webs laminatedtogether to form stacks. In some cases, these optical web stacks arelaminated in a manner that allows upper web layers to be peeled or tornaway from the remaining layers. The individual optical web layers of thelaminated stacks may be identical to one another, but in some cases theyare different. For instance, the optical web may include stack having abase web layer and one or more releasable web layers laminated to thebase layer. The base web layer may have a thickness, or a rigidity thatis greater than that of the other web layers. In such a case, theresulting laminated optical web stack may be suitable to be used as afinal product, such as a face mask, that can be applied to a garmentlike a hood, or inserted into a frame of a goggle assembly. Additionallyand/or alternatively, the optical web product can be applied topre-existing windows, such as a pre-existing goggle assembly or apre-existing face mask, for example, via an adhesive applied to a lowerlevel of the stack. Either way, whether applied to a pre-existing windowor serving as a window itself, the individual layers of the stack can belaminated via a peelable adhesive that allows a user to peel away andremove the outer-most lens, thereby exposing a lower lens to provide aclear field of view.

The optical webs can be used in protective eyewear or other protectiveoptical structures, such as goggles, face shields, masks, helmets,glasses, windows, windshields, or the like. The optical webs can besterilized, for example, using chemical and/or gamma sterilizationtechniques, and used in a sterile environment, such as a surgicalenvironment or the like. The optical webs are designed to replace otherwebs or substrates that are not coated in the manner descried herein,such that the optical web would reflect less light than the substratealone.

In one example, an optical web comprises a substrate that includes anoptical material (e.g., a polymer) that is clear or transparent.Throughout this application, the term “transparent” should be understoodto refer to material that can be seen through. While the term may referto material that is perfectly transparent, it also encompasses othersee-through materials including tinted materials, colored materials,translucent materials, hazy or frosted materials, and the like.

The substrate has a refractive index value, which is typically largerthan the refractive index of air, (i.e., about 1.00). The optical webincludes first optical coating applied to one side (e.g., the anteriorside) of the substrate. The first optical coating can also be made froman optical material (e.g., a polymer) that is clear, transparent, orotherwise see-through. The first optical coating has its own refractiveindex value, different from that of the substrate. For example, thefirst optical coating can have a refractive index value that is lessthan that of the substrate but still larger than 1.00.

In some examples, the first optical coating is also applied to theopposite side (e.g., the posterior side) of the substrate. However, inother examples, the opposing side may be coated with a different opticalcoating, or not coated at all. For instance, the opposite side of thesubstrate may be coated with a second optical coating having a differentrefractive index from that of the first optical coating, or it may becoated with an AR coating. This AR coating can be applied afterconversion of a roll of an optical web to a final shape (e.g., a faceshield) so that the AR coating need not be applied to the entire web.

The optical web may further include additional optical coating layersapplied to the first optical coating and/or the second optical coating.For instance, the optical web may include a stack of two, three, four,or more optical coating layers applied on the substrate. Where multiplecoating layers are applied, the coatings can be arranged so that therespective refractive indexes decrease monotonically from the substratetoward the outer layers.

FIGS. 1 and 2 show an embodiment of such an optical web 100. FIG. 1provides an isometric view of the optical web 100, and FIG. 2 provides aside elevation view of the web 100. The optical web 100 includes asubstrate 102, which can be formed from a variety of film materials. Forinstance, the substrate 102 can include or be formed from polycarbonate,acrylic, PMMA, polyethylene terephthalate (PET), or biaxially-orientedpolyethylene terephthalate (BoPET), such as a product commercially knownas Mylar, for example.

The substrate can be of any thickness, but is generally at least thickenough so as not to be considered a thin film, that is, a film with athickness on the order of the wavelength of visible light. For example,the thickness of the substrate is generally greater than 2 microns (2000nm), but can also be considerably larger, for example, 0.05 mm (about 2mils), 0.1 mm (about 4 mils), 0.2 mm (about 8 mils), 0.4 mm (about 16mils) or larger. The substrate can be flexible or stiff, but isgenerally flexible enough to be applied through a lamination process andkept as a roll material. Depending on the material used, the substrate102 will have a substrate refractive index value. The substraterefractive index will be larger than that of air (1.00). In someexamples, the substrate refractive index will be larger than 1.46, oreven 1.50, and in some examples, will be at least about 1.53. In someexamples, such as when the substrate is formed from BoPET, therefractive index may be about 1.64 to about 1.67. As noted in table 1,substrates having a refractive index of 1.65 will have a totalreflectance of 6.02% on one surface.

To reduce the reflectance, the optical web 100 comprises an anteriorcoating 104 coated on an anterior surface of the substrate. The anteriorcoating 104 is formed from a material that has a refractive index lessthan that of the substrate 102, though still larger than 1.00. Forinstance, the anterior coating 104 can be formed from a polymer orplastic material, such as PET, BoPET, PMMA, acrylic, silicones,flourimers, or polycarbonate. The anterior coating 104 can be relativelythin compared to the substrate 102, but not so thin that it would beconsidered a thin film with a thickness on the order of the wavelengthof visible light. For instance, the coating may be at least four timesgreater than the wavelength of visible light, and in some cases at leastabout 2 microns (i.e., 2000 nm) thick. In some instances, the anteriorcoating 104 may be considerably thicker, and may even have a thicknessof about 1%, 10%, 25%, or 50% of that of the substrate 102. In someexamples, the thickness of the anterior coating 104 (or any coatinglayer) will be negligible compared to the thickness of the substrate102. In some instances, the coating may be an adhesive or a low surfaceenergy material that facilitates the attachment of the web to anothersurface.

Generally, the coating 104 will be a transparent coating, and in someinstances, may be clear and/or colorless. In some examples, the anteriorcoating 104 may be configured to provide additional properties. Forexample, the coating 104 may provide hardening or scratch resistantproperties to the optical web 100.

The anterior coating 104 can have a refractive index between about 1.40and about 1.50. In some examples, the anterior coating will have arefractive index no greater than about 1.46. In some examples, theanterior coating 104 may have a refractive index between about 1.33 andabout 1.42. In other examples, the anterior coating 104 may have arefractive index as low as 1.30, or lower. The anterior coating 104creates an interface with the substrate, which in turn generates acertain amount of reflectance. For example, where the refractive indexof the substrate is 1.65, and the refractive index of the coating is1.40, the total reflectance from the anterior side of the optical web100 will be about 3.45%. This is determined by adding the reflectancegenerated by each interface between the coating and the substrate, andbetween the coating and air.

The interface between the coating and the substrate reflectance iscalculated as:

$R_{1} = {{\frac{1.65 - {{1.4}0}}{1.65 + {{1.4}0}}}^{2} = {{0.6}7\%}}$

The interface between the coating and air reflectance is calculated as:

$R_{2} = {{\frac{1.40 - {{1.0}0}}{1.40 + {{1.0}0}}}^{2} = {{2.7}8\%}}$

The total reflectance is calculated by adding R₁ and R₂ to arrive at3.45%. Thus, the application of the anterior coating drops thereflectance by 2.57%, from 6.02% to 3.45%. This value is shown below inTable 2, which also shows the resulting reflectance in one directionwhen coatings having different refractive indexes are applied to asubstrate having a refractive index of 1.65.

TABLE 2 Reflectance % Reflectance % from Total RI of from coatingcoating to Reflectance RI of RI of Coating to air substrate (One AirSubstrate Layer interface interface Direction) 1.00 1.65 1.25 1.23%1.90% 3.14% 1.00 1.65 1.30 1.70% 1.41% 3.11% 1.00 1.65 1.33 2.01% 1.15%3.16% 1.00 1.65 1.35 2.22% 1.00% 3.22% 1.00 1.65 1.40 2.78% 0.67% 3.45%1.00 1.65 1.42 3.01% 0.56% 3.57% 1.00 1.65 1.45 3.37% 0.42% 3.79% 1.001.65 1.46 3.50% 0.37% 3.87% 1.00 1.65 1.50 4.00% 0.23% 4.23% 1.00 1.651.52 4.26% 0.17% 4.43%

Table 2 shows the reflectance from one side of the optical web 100, forexample, the anterior side with a coating, but does not consider thereflectance from the opposing side of the optical web 100. To reducereflectance on the opposite side, the optical web 100 may also include aposterior coating 106 on the posterior side of the substrate 102. FIGS.1 and 2 also show such a posterior coating 106 coated on the posteriorsurface, which is opposite the anterior side.

Like the anterior coating 104, the posterior coating 106 is formed froma material that has a refractive index less than that of the substrate102, but larger than 1.00. The posterior coating 106 (and all coatingsand coating layers described throughout this application) may be formedfrom the same or similar materials that are described above with respectto anterior coating 104. For instance, the posterior coating 106 may bean adhesive or low surface energy material that allows the web to attachto another surface, such as a window. The posterior coating 106 may havesimilar parameters to the anterior coating 104, such as coatingthickness, refractive index, color, and transparency. As with anteriorcoating 104, the posterior coating 106 has a thickness large enough tonot be considered a thin film, but may nevertheless still be relativelythin (e.g., at least one micron thick). Where the posterior coating 106has the same parameters as those described above for the anteriorcoating 104, then the total reflectance from the posterior side of theoptical web 100 will be the same as that for the anterior side. In theabove example, where the substrate has a refractive index of 1.65 andthe posterior coating has a refractive index of 1.4, then the totalreflectance from the posterior side will also be 3.45%, which would makethe total reflectance of the optical web 6.90%. This is significantlyreduced from the 12.033% reflectance of the substrate alone.

In other embodiments, the posterior coating 106 has different parameters(e.g., thickness, material, refractive index, etc.) from the anteriorcoating 104. For example, the posterior coating 106 can have arefractive index value between 1.40 and 1.50. In some instances, theposterior coating may have a refractive index no greater than about1.46. The posterior coating 106 may have a refractive index between 1.33and 1.42, and in some instances, may be as low as 1.30 or lower. In someexamples, the posterior coating 106 may be or include an AR coating, forinstance, where the coating can be applied to a relatively small surfacearea, and/or where the mitigation of reflections through the surface isimportant. In other examples, the optical web 100 may not have anyposterior coating. In further examples, the posterior coating 106 and/orthe anterior coating 104 may be further coated with an AR coating tofurther reduce reflections.

In some forms, the optical web 100 may include additional coating layersapplied to the substrate. For instance, the optical web 100 may includetwo or more anterior coating layers and/or two or more posterior coatinglayers applied to the substrate. The multiple coating layers are appliedin a manner such that successive outer layers have lower refractiveindexes than the coating layers inward, or closer to the substrate. Thatis, the coating layers are applied to be monotonically decreasing inrefractive index moving outward from the substrate.

FIG. 3 shows a side view of an example of an optical web 300 thatutilizes multiple optical anterior and posterior coatings on a substrate302. In particular, the optical web 300 includes a substrate 302, with acoating stack 310 applied to one side of the substrate 302. The coatingstack 310 includes a plurality of coating layers, including a firstcoating layer 312 applied to the substrate and a second coating layer314 applied on the first coating layer 312. The coating stack 310 isshown having just two layers, but more layers could be utilized,including three layers (as shown FIG. 4 ), four, five, or more layers.Moreover, as discussed above with respect to FIGS. 1 and 2 , the coatingstack 310 could have just one coating layer. In this embodiment, thesecond coating layer 314 serves as the outer most coating layer of theoptical web.

The coating layers each have a different refractive index that decreasesmonotonically away from the substrate. That is, in FIG. 3 , therefractive index of the first coating layer 312 is less than therefractive index of the substrate 302, but greater than the refractiveindex of the second coating layer 314. Where additional coating layersare applied to the coating stack 310, those successive coating layerswill have refractive indexes that are less than those of the coatinglayer to which they are applied, such that the outer most coating layerwill have the lowest refractive index of all the coating layers of thestack 310. Such an outermost coating layer would constitute the anterior(or posterior) surface of the optical web.

In some examples, one or more of the coating layers may be configured toprovide additional properties. For example, one or more coating layers,in particular, the outermost coating layer may be a hard coating thatprovides scratch resistant properties to the optical web 300. Thecoating layers can also be used to provide anti-fogging properties, oranti-fingerprint properties. In some cases, the coatings themselves willnot provide any other functionality, but may instead be further coatedwith an additional coating layers that is not considered a part of thecoating stack 310 or the optical web 300. These additional functionalcoating layers may have refractive indexes that do not necessarilycomply with the monotonically decreasing refractive index values of theweb, but are nevertheless considered within the scope of the describedexamples.

When multiple coating layers are applied to an optical web, thereduction in reflectance can be even further reduced, as shown in Table3. Specifically, Table 3 shows the reflectance that results from eachinterface of a two-layer coating stack applied to a substrate having arefractive index of 1.65.

TABLE 3 Reflectance Reflectance Reflectance Total RI RI of RI of % Outer% Outer to % Inner Reflectance of RI of Inner Outer Coating to InnerCoating to % (One Air Substrate Coating Coating Air Coating SubstrateDirection) 1 1.65 1.46 1.3 1.70% 0.34% 0.37% 2.41% 1 1.65 1.46 1.321.90% 0.25% 0.37% 2.53% 1 1.65 1.46 1.4 2.78% 0.04% 0.37% 3.20% 1 1.651.46 1.48 3.75% 0.00% 0.37% 4.12% 1 1.65 1.46 1.52 4.26% 0.04% 0.37%4.67% 1 1.65 1.42 1.3 1.70% 0.19% 0.56% 2.46% 1 1.65 1.42 1.32 1.90%0.13% 0.56% 2.60% 1 1.65 1.42 1.4 2.78% 0.01% 0.56% 3.34% 1 1.65 1.421.48 3.75% 0.04% 0.56% 4.35% 1 1.65 1.42 1.52 4.26% 0.12% 0.56% 4.93%

For the first five samples of Table 3, the inner coating (i.e., thelower-most coating applied to the substrate) has a refractive index of1.46. For the second five samples, the inner coating has a refractiveindex of 1.42. Where the outer coating is monotonic (i.e., where therefractive index of the outer coating is less than that of the innercoating), the total reflectance is reduced from that of just a singlecoating layer. For example, in comparing the results of Table 2 for acoating layer of 1.46, which has a reflectance of 3.87 with those ofTable 3 that use a monotonically decreasing refractive index outerpolymer (i.e., coatings with RI of 1.3, 1.32, and 1.4), the totalreflectance is always less than 3.87. However, where the outer coatinglayer is not a monotonic decrease (i.e., RI of 1.48 and 1.52), thereflectance is actually higher than if no second coating layer wereapplied. The same results hold true in comparing the reflectance for acoating of 1.42 in Table 2 with those that use an inner coating with anRI of 1.42 in Table 3.

In some examples of a two-coating stack, the interface between air andthe outer coating provides the greatest index differential, therebybeing the source for the greatest amount of reflectance. Accordingly,decreasing the outer coating layer, or the layer forming the anteriorside (or the posterior side) of the optical web will have a maximumvalue. For instance, in some examples, the refractive index of the outercoating layer forming an anterior side of the optical web will be nogreater than about 1.46. In other cases, the outermost coating formingthe anterior side of the optical web will be no greater than 1.42, oreven 1.40. In some instances, the refractive index of the outer coatinglayer will be between about 1.33 to about 1.42, which provides asuitably low refractive index while still allowing the coating to bereadily formed from available materials. In some instances, the outercoating layer may be even less, though it may be costlier to generatecoatings having lower refractive indexes. In one particular example, anoptical web having a coating stack with two optical coating layerscomprises a substrate with a substrate refractive index of at leastabout 1.53, and the first coating (i.e., the inner coating layer) has arefractive index of between about 1.44 and about 1.48, and the secondcoating (i.e., the outer coating layer) has a refractive index nogreater than about 1.43.

As shown in Table 3, applying two monotonic decreasing coating layersfurther reduces the reflectance of the optical web. Applying more layers(e.g., three layers, four layers or more) will still further reduce thereflectance as long as the layers are applied in a monotonicallydecreasing manner. Thus, some examples of the optical webs describedherein will include coating stacks that apply three, four, five or morecoating layers on a substrate. There is no limit to the number ofcoating layers that can be applied.

Moreover, coating stacks having multiple coating layers can be appliedon both sides of a substrate to further reduce reflectance. For example,FIG. 4 shows an optical web 400 including a substrate 402 that has ananterior coating stack 410 with three coating layers 412, 414, and 416applied on an anterior side, and a posterior coating stack 420 with twocoating layers 422 and 424 applied on the posterior side of the stack420. The layers of each stack 410 and 420 are selected to haverefractive indexes that decrease monotonically moving away from thesubstrate in either direction.

As noted above, some embodiments include a laminated stack of tear-offlens layers, whereby each of the lens layers is formed from an opticalweb consistent with one of the examples described above. That is, thelens layers of the stack are formed with a substrate having at least onecoating layer, whereby the coating layers have refractive indexes thatmonotonically decrease moving outward.

FIG. 5 shows an example of a laminated optical web 500 comprising fiveseparate layers, including a base layer 501, and four removable layers502 a-d, each held together via a peelable adhesive 510 a-d. Each of theremovable layers 502 n and the base layer 501 can have a configurationconsistent with any of the examples of optical webs described herein.That is, (though not specifically shown in the Figure) each individuallayer of FIG. 5 includes a substrate and at least one first coatinglayer (e.g., on the anterior side), where the coating layer has a lowerrefractive index than that of the substrate. Each layer can also includea second coating layer on the opposite side of the substrate from thefirst coating layer (e.g., on the posterior side). Further, each coatinglayer can include a coating stack comprising multiple coating layerswith refractive indexes that reduce monotonically moving outward fromthe substrate.

It should be noted that while the example stack 500 is shown having asingle base layer 501 and four releasable layers 502 n, other examplescan include more or fewer releasable layers 502, such as two, three,four, ten, twenty, fifty, or more layers, depending on the intendedapplication and use for the stack 500.

Adhesive layers 510 n are applied between the various layers of the lensstack 500. The adhesive layers 510 n can be formed from an adhesive thatallows an upper layer to be peelably released from the lower layer. Theadhesive layers 510 can also be configured to remain with the releasedlayer to avoid leaving an adhesive residue on the newly exposed surface.For example, when releasable layer 502 d (i.e., the outermost layer) ispeeled away from the stack, adhesive layer 510 d will remain attached toreleased layer 502 d so that little or no adhesive residue remains onthe outer surface of the newly exposed layer 502 c. The adhesive formingthe adhesive layers 510 n can be or can comprise an acrylic adhesive,silicone, or another adhesive that provides for a peelable adhesionbetween layers.

The adhesive is also selected to have refractive index that is closelymatched to the refractive index of at least one of the substrate and/orthe coating layers of the releasable layers 502 n and the base layer501. For example, the adhesive can be selected to have a refractiveindex that is matched to within about 0.2 of the refractive index of thesubstrate. In other examples, depending on the amount of reflectancedesired, the adhesive is selected to have a refractive index that has aneven tighter match to the refractive index of the substrate, forinstance to within about 0.15, 0.12, 0.10, 0.08, 0.05, or 0.02. Matchingthe refractive index of the substrate of the releasable layers 502 n andthe base layer 501 helps mitigate internal reflections caused by theinterfaces between the optical web layers and the adhesive.

An attaching adhesive 520 may be applied to a lower surface of the baselayer 501. The attaching adhesive 520 is configured to attach the lensstack 500 to a surface such as a window, shield, or display, so as toprotect the surface. The attaching adhesive 520 may be configured tohave a stronger peel force than the releasable adhesive layers 510 nsuch that the lens stack 500 remains solidly adhered to the surface evenwhen the releasable layers are peeled away. The attaching adhesive layer520 may be configured to form a more “permanent” adhesion, but in someexamples, the attaching adhesive layer 520 is also configured to bereleasable, such that the adhesive 520 remains with the base layer 501when the base layer and/or the lens stack 500 is removed from thesurface. In some examples, the attaching adhesive layer 520 may be thesame as the releasable adhesive layers 510 n. Some examples of the lensstack 500 may include protective liner 525 that protects the attachingadhesive 520 prior to its application onto a surface. The attachingadhesive 520 may be a self-wetting or dry mount adhesive thatfacilitates removal of air between the stack 500 and the surface afterapplication, for example, by applying pressure across the surface of thestack. Examples of such a self-wetting/dry mount adhesive are describedin U.S. Pat. No. 9,295,297, which is hereby incorporated by reference inits entirety. The refractive index of the attaching adhesive may also bematched to the refractive index of the components optical webs 501 and502 n and/or the releasable adhesive layers 510 n (e.g., to within about0.2 about 0.12, about 0.02, etc.).

Some examples of the lens stack 500 will not include an attachingadhesive 520 or a liner layer 525. In such an example, the lens stackmay be configured to serve as a window (e.g., a face shield, eye shield,or other optical device) itself, without attaching to another surface.In some examples, the base layer 501 of the stack 500 may have athickness that is greater than that of releasable layers 502 n toprovide added stiffness/rigidity to the stack 500. For example, the baselayer may have a thickness of about 0.2 mm (about 8 mils), and thereleasable layers 502 may have a thickness of about 0.05 mm (about 2mils). In another example, the base layer 501 has a thickness of about0.1 mm (about 4 mils), and the releasable layers 502 have a thickness ofabout 0.05 mm (about 2 mils). In general, the thicknesses of the variouslayers can vary widely depending on the intended application of the lensstack 500. For example, either the base layer 501 or the releasable lenslayers 502 may have thicknesses in the range between about 0.025 mm(about 1 mil) and 0.4 mm (about 16 mils), or larger. In some examples,the thicknesses of the various releasable layers 502 can also vary.

The optical webs and lens stacks described herein can be used to formvarious optical devices, such as shields for protecting a wearer's faceand eyes or for protecting display surfaces, such as for smart phonesand tablets, televisions, or other screens. The optical webs can beformed as a rolled sheet or stack of material, as shown in FIG. 6A.Specifically, FIG. 6A shows an optical web 600 provided as a roll 602 ofmaterial wound about an axis. The optical web 600 can be any of theoptical webs described herein, or it may include a stack of optical webslaminated together as shown with respect to FIG. 5 . The optical web 600on the roll 602 can subsequently be processed by being laminated withother webs, or by being converted from the sheet.

FIG. 6B shows an example of the optical web 600 being cut by stampingdevices 620, which press down on the web 600 to cut and form two opticaldevices 610, which can form a window or shield, for example. In someexamples, the optical device 610 can then be attached to components thatare used for other purposes, such as a frame for an eye protector, or agarment, sheath, or other material used to protect a wearer.

FIG. 6C shows an example of the optical shield 610 attached to amaterial 630 such that the garment surrounds the shield 610. Thematerial 630 can be used to form, for example, a medical garment used toprotect medical caregivers in a surgical environment. The material 630may include a breathable fabric that can be formed into a covering thatis designed to be sterilized and placed over a wearer's head and usedduring surgery. Because the optical shield 610 is formed from the lowreflectance optical webs described herein, the medical caregiver canhave an improved visibility throughout while performing the surgery.Moreover, because the reduced reflectance is achieved without requiringthe use of costly AR coatings or other thin film features, the shieldscan be cost-effectively mass produced on roll stock as described herein.Further, the optical webs and garments can be formed from higher indexpolyester materials that are capable of being sterilized using a varietyof sterilization techniques (e.g., gamma radiation), without beingsubjected to deformation, discoloration, or other visibility impairingissues. That is because the described webs can be formed from substratesthat have higher refractive indexes capable of withstandingsterilization techniques like gamma radiation, while reducing the glareand other issues that would otherwise result from the use of a higherindex material.

In medical settings, spatter and other projectiles in the form ofbiological material can be a hazard, for instance, where proceduresinvolve aggressive sawing or cutting actions that cause bone, tissue,blood, and/or other fluids to project toward the face and eyes of thecaregivers. In such situations, the medical caregivers (e.g., doctors,surgeons, nurses, technicians, etc.) may wear protective garments in theform of goggles, masks, or the like, to protect their eyes. As such, itcan be useful to provide the protective garments, such as garment 650disclosed with respect to FIG. 6C, with a shield 610 that is in the formof a laminated tear-off stack as described herein. Using the laminatedstacks helps the caregiver to retain a clear, unsoiled field of vision,but because these stacks often include several layers, the interfacesbetween these layers can create reflections that increase the glarethrough the shield, making it difficult for the caregiver to see withthe visual acuity necessary to perform the medical tasks. This isparticularly true where the caregiver is wearing a lighting deviceunderneath the garment, which is often necessary to ensure the sterilityof a medical or surgical environment. Using the reduced reflectancetechnology described herein, the amount of reflections can be reduced,thereby limiting glare and improving the viewability through thegarment.

This application also describes examples of methods and processes formaking the optical webs and other garments described herein. FIGS. 7Aand 7B are flow diagrams of methods for manufacturing an optical web.FIG. 7A shows an example of one method 700 of forming an optical webcoated on both the anterior and posterior side. First, a substrate isprovided 702 or obtained. The substrate can be provided as a roll ofmaterial, or as an individual component. The substrate can be generallytransparent, and will have a refractive index. For instance, thesubstrate can include PET, BoPET, polycarbonate, acrylic, or anotherpolymer. A coating is then applied 704 to an anterior side of thesubstrate. The coating can be any of the coatings described herein. Thecoating is selected to have a refractive index that is less than that ofthe substrate. A posterior coating is also applied 706 to the posteriorside of the substrate. The posterior coating can be the same as theanterior coating, or it can be different, but the refractive index ofthe posterior coating is less than that of the substrate. In someexamples, both the anterior coating and the posterior coatings arecoating stacks that include two or more coating layers withmonotonically decreasing refractive indexes. Providing coatings in thismanner on both sides of the substrate decreases reflectance from eachside of the optical web. It should be noted that in method 700, thecoatings can be applied in no particular order. For example, theanterior coating can be applied 705 before, after, or concurrent withthe application 706 of the posterior coating layer.

FIG. 7B shows an example of a method 750 that applies a stack comprisinga plurality of coating layers to one side of an optical web. First, asubstrate is provided 752 or obtained. As with step 702 of method 700,the substrate can be provided as a roll of material, or as an individualcomponent. The substrate can be generally transparent, and will have arefractive index. For instance, the substrate can include PET, BoPET,polycarbonate, acrylic, or another polymer. A first coating is thenapplied 654 to either an anterior or posterior side of the substrate.The coating can be any of the coatings described herein. The coating isselected to have a refractive index that is less than that of thesubstrate. A second coating layer is applied 756 to the first coatinglayer. The second coating layer has a refractive index less than that ofthe first coating layer and the substrate. Further coatings can beapplied to the web in subsequent steps, such that the coatings haverefractive indexes that decrease monotonically away from the substrate.In some examples, rather than applying a layer first to the substrate,the method 750 may first include forming a stack of multiple coatinglayers having monotonically decreasing refractive indexes, and thenapplying the stack of coating layers to the substrate. In otherexamples, a coating layer or a coating stack can also be applied to theopposite side of the substrate.

In some examples, the webs made by the described methods can belaminated together to form laminated tear-off stacks and/or cut orconverted to form optical devices such as shields and windows. Infurther examples, additional coating layers, such as hard coats, scratchresistant coatings, anti-fingerprint coatings, anti-glare coatings,matte coatings, friction reducing coatings, or the like can be appliedto the optical webs. These additional functional coatings may be a partof the monotonically reducing refractive index coating stacks, or theymay be separate coatings that do not necessarily have refractive indexeslower than the outermost layer of the web.

FIGS. 8A and 8B are diagrams comparing the reflectance of two opticalwebs. In FIG. 8A, an optical web 800 a comprises only a substrate 802 a.The substrate 802 a forms a first interface A with the air and a secondinterface B with the air. Each of these interfaces creates a reflectionthat reflects light back toward an eye 10 of a wearer. The reflectionsare represented by vectors 831 and 832. Because the substrate has nocoating, the reflectance will depend on the difference in the refractiveindex between the substrate (e.g., 1.65 for an uncoated Mylar) and air(about 1). Each surface will generate a separate reflection. Because thedifference in refractive indexes is relatively high, each surface willgenerate a relatively high percentage of light, which will depend on thespecific refractive index and the angles of incidence and refraction.For normal incidence angles and a substrate having a refractive index of1.65, reflectance values are demonstrated in Table 1.

FIG. 8B shows an optical web 800 b having coating stacks 810 and 820applied on both sides of a substrate 802. Each coating stack has twocoating layers, for instance, the anterior coating stack includes aninner anterior coating layer 822 and an outer anterior coating layer824. And the posterior coating stack 810 includes an inner posteriorcoating layer 812 and an outer posterior coating layer 814. The layersare arranged so that the refractive indexes of the coatings decreasemonotonically moving away from the substrate 802. That is, the inneranterior coating layer 822 refractive index is less than that of thesubstrate 802, but greater than that of the outer anterior coating layer824. Likewise, the inner posterior coating layer 812 is less than thatof the substrate 802, but greater than that of the outer posteriorcoating layer 814. The layers forming the anterior stack 820 and theposterior stack 810 may be the same and may have the same refractiveindex values, but they may also be different from one another. FIG. 8Balso shows that each interface, between air and the outer coatinglayers, between the inner and outer coating layers, and between theinner coating layers and the substrate each generate a reflectiondepicted by a vector line (841-846). Because the refractive index of theouter coating layers 814 and 824 are less than that of the substrate,and therefore closer to the refractive index of air (about 1), theresulting reflections 841 and 846 will be less than those of reflections831 and 832 from FIG. 8A. As explained above with respect to Table 3,the resulting reflections from the remaining interfaces will contributesome reflectance, but the resulting reflectance is still less than thatof the embodiment of FIG. 8A.

The described examples provide a low-cost reflectance reducing coatingsfor disposable polymer lenses, in particular, lenses that can beprocessed on a roll to roll web. The described webs are suitable for useas disposable lenses for use in sterile surgical environments, which aremost cost effective when processed by roll to roll web processes. Thelens substrate of choice for such applications is a polyester because itdoes not discolor from gamma sterilization as does other lens materialsuch as polycarbonate and PMMA (Acrylic). And while polyester (e.g.,BoPET) handles effectively in roll to roll web processing and can begamma sterilized, the high index of refraction of polyester can causehigher levels of unwanted reflection, for example, in the range of about12-13% or even higher. The reflection is a significant distraction tothe user of the lens system. The described techniques and webs allow forthe production of a cost-effective, disposable, low reflection lenssystem that also meet the other useful criteria in the medical field andother environments. The described embodiments can be employed withoututilizing AR coatings formed from thin films as described above.

As noted above, this application claims priority to, and incorporates byreference U.S. provisional patent application No. 62/367,845, whichrelates to touch screen protectors and shields that have an AR coatingapplied to an underside of the protector, such that, when applied, thesurface of the shield with the AR coating faces the touch screen.Examples of such screen shields and protectors are described furtherbelow.

In some examples, touch screen protective shields are configured toadhere to the touch screen around a peripheral edge of the touch screen.The central portion of the shield is generally free of adhesive, andthus does not adhere to the active display portion of the shield. Thecentral portion of the shield may be lifted off or spaced away fromtouch screen, for example, by way of a thick border adhesive, an annularspacer layer, and/or tension applied to the shield when being attachedto the touch screen.

An AR coating is applied to the underside of the shield, i.e., theshield surface that faces the touch screen when attached thereto. The ARcoating inhibits formation of Newton rings and other unsightlyinterference patterns that may otherwise result when two surfaces (e.g.,the inner surface of the shield and the touch screen surface) come intocontact or close proximity with one another. Because the AR coating isprovided on the underside surface of the shield, it remains protected bythe outer surface of the shield, the adhesive, and the touch screenitself, and thus is not subject to fingerprints, smudging, breaking, orother damage that can otherwise occur on AR coatings.

One example of such a protective shield includes a shield for anelectronic device, where the electronic device has a touch screen with adisplay area surrounded by a border region. The shield has an inner sideand an outer side, and the shield defines a perimeter portion thatcorresponds to the border region of the touch screen and a centralportion that corresponds to the display area of the touch screen,whereby the perimeter portion surrounds the central portion. The shieldcomprises a base layer having an outer surface and an inner surface. Theshield also comprises an adhesive layer applied about the perimeterportion of the inner side of the shield, and an AR coating applied tothe inner side of the shield. The shield, the perimeter portion of theshield, the central portion of the shield, and the applied adhesivelayer are configured to attach the shield to the touch screen of thedevice so that the adhesive layer is disposed on the border region ofthe touch screen, so that the display area of the touch screen isvisible through the central portion of the shield, so that the innersurface of the base layer does not adhere to the display area of thetouch screen, and so that the touch screen maintains touch sensitivitythrough the attached shield.

In some embodiments, the AR coating on the shield is configured toinhibit the reflection of at least some light that projects from thetouch screen by the shield. The AR coating may also be configured toinhibit the appearance of interference patterns. In some forms, the ARcoating is configured so that it is not detectable to a human eye whenattached to the touch screen, and/or so that touch sensitivity of thetouch screen is not inhibited.

The base layer of the shield may comprise glass, and the AR coating maybe applied to the shield at a high temperature so as to increase thedurability of the AR coating. Alternatively, the base layer may includea flexible film material, such as a plastic material, e.g., PET. In someforms, the AR coating can be applied at a cool temperature. The ARreflective coating may be fragile or otherwise subject to absorb damagewhen exposed to frequent touching. The AR coating may include multiplelayers (e.g., 8 layers), and individual ones of the multiple layers maybe configured to inhibit the shield from reflecting light having aparticular range of wavelengths.

In some examples, base layer is flexible and configured to conform to atouch screen having a curved surface.

The shield may be configured to be removable from the touch screen. Insome examples, the adhesive layer and the outer surface of the baselayer are configured to protect the AR coating from coming into contactwith environmental objects.

The shield may include a hard coat on the outer side of the shield. Thebase layer may comprise a hard coat on the outer surface of the baselayer.

In some forms, the AR coating is applied directly to the inner surfaceof the base layer. Further, the AR coating may be applied only to thecentral portion of the shield.

In some embodiments, the shield comprises a mask layer applied about theperimeter portion of the shield. The mask layer may be is opaque and isconfigured to hide, mask, or disguise optical artifacts generatedbetween the border region of the touch screen and the shield. The maskcan be about 0.2 mils thick. In some examples, the adhesive layer isapplied to the mask layer.

In some examples, the base layer comprises a plurality of layers. Forinstance, the base layer may include comprises an outer base layerlaminated to an inner base layer. The outer base layer can be formedfrom PET and have a hard coating on the outer surface of the base layer.The outer base layer may be about 3 to about 4 mils thick in someembodiments. For example, the outer base layer can be about 3.5 milsthick. The inner base layer can be formed from PET and comprises an ARcoating on the inner surface of the base layer. The inner base layer canbe about 3 to about 4 mils thick, for instance, about 3.5 inches thick.

The base layer can comprise or be formed from at least two differentmaterials. The base layer can have a beveled edge.

In some examples, the adhesive layer comprises a carrier. The adhesivelayer can be about 3 to about 4 mils thick, for instance, about 3.5 milsthick.

The total thickness of the shield itself, in some embodiments, is about10 to about 11 mils thick. In some forms, the shield is about 0.0107inches thick.

Some examples of the shield include cutouts that correspond to featureson the touch screen, such as cutouts that correspond to one or more of alight, a speaker, and a button on the touch screen.

The shield is configured so that the touch screen maintains touchsensitivity through the attached shield. In some examples, at least aportion of the perimeter portion of the shield is opaque to mitigatevisibility of optical artifacts between the touch screen and theattached shield. For example, at least one of a perimeter portion of thebase layer or the adhesive may be opaque.

In some examples, the adhesive layer is sufficiently thick to lift theinner surface of the base layer off the display area of the touchscreen. In some embodiments, wherein the adhesive layer is configured totrap air between an attached shield and the display area of the touchscreen, and the trapped air can be configured to form a planar airbearing.

In some examples, the shield comprises a spacer interposed between theinner surface of the base layer and the adhesive layer. The shield canbe arranged so that, wherein the combined thickness of the spacer layerand the adhesive layer is sufficient to lift the inner surface of thebase layer off the display area of the touch screen.

In some examples, the electronic device is arranged so that a majorityof the active area and the inactive area of the touch screen share acommon plane, and wherein a lower surface of the central portion of thebase layer of an attached shield is in a different plane from thatshared by the majority of the active area and the inactive area.

In some examples, the AR coating comprises at least one layer, andwherein individual ones of the at least one layer have a thickness thatis about one quarter of the wavelength a particular type of visiblelight. The AR coating may include a ceramic substance. The AR coatingcan include multiple layers, (e.g., 8 layers). In some forms, thevarious layers of the AR coating each have a width that corresponds to aparticular wavelength of light in the spectrum of visible light. In someexamples, each of the layers of the AR coating have a differentwavelength.

Examples of such shields are shown and described in U.S. provisionalpatent application No. 62/367,845, which is hereby incorporated byreference in its entirety, and to which this application claimspriority.

This application describes preferred embodiments and examples of opticalwebs with coatings designed to reduce the refraction and reflection oflight. Those skilled in the art will recognize that a wide variety ofmodifications, alterations, and combinations can be made with respect tothe above described embodiments without departing from the scope of theinvention as set forth in the claims, and that such modifications,alterations, and combinations are to be viewed as being within the ambitof the inventive concept. In addition, it should also be understood thatfeatures of one embodiment may be combined with features of otherembodiments to provide yet other embodiments as desired. In particular,it should be understood that all embodiments described herein can beapplied to, and used in connection with the embodiments of othertear-off lens configurations. All references cited in the presentdisclosure are hereby incorporated by reference in their entirety, asare all references that are, in turn, incorporated by reference in thosereferences.

What is claimed is:
 1. An optical web comprising: a substrate having asubstrate refractive index, the substrate having an anterior side and anopposing posterior side; an anterior coating including a plurality ofcoating layers, individual coating layers having individual refractiveindexes, a first anterior layer applied to the anterior side of thesubstrate, the first anterior layer having a first anterior layerrefractive index, wherein the individual coating layers are arranged sothat the individual refractive indexes of successive individual coatinglayers decrease in a monotonic function from a base layer toward ananterior side of the optical web, and the individual refractive index ofan individual coating layer forming the anterior side of the optical webis no greater than about 1.46, a posterior coating including a firstposterior layer applied to the posterior side of the substrate, thefirst posterior layer having a first posterior layer refractive index,wherein the substrate refractive index is greater than the firstanterior refractive index and the first posterior refractive index andthe substrate refractive index is at least about 1.53.
 2. The opticalweb of claim 1, wherein the posterior coating comprises a secondposterior layer applied to the first posterior layer, the secondposterior layer having a second posterior refractive index that is lessthan the first posterior refractive index.
 3. The optical web of claim1, further comprising an adhesive layer laminated to at least one of theanterior or posterior side, the adhesive layer comprising a refractiveindex matched to within about 0.2 of the substrate refractive index. 4.The optical web of claim 1, wherein the first anterior layer refractiveindex is between about 1.40 and about 1.46.
 5. The optical web of claim1, wherein the optical web is wrapped about an axis to form a roll ofweb material.
 6. The optical web of claim 1, wherein the substratecomprises biaxially-oriented polyethylene terephthalate (BoPET).
 7. Theoptical web of claim 1, wherein the substrate comprises polycarbonate oracrylic.
 8. The optical web of claim 1, wherein the first anterior layercomprises a polymer with a low index of refraction.
 9. The optical webof claim 1, wherein the substrate has a thickness of at least about 2microns.
 10. The optical web of claim 9, wherein the first anteriorlayer and the first posterior layer have a thickness greater than about2 microns.
 11. A shield for a garment comprising a cut portion of theoptical web of claim
 1. 12. The shield of claim 11, wherein the shieldhas been sterilized using gamma radiation.
 13. The shield of claim 12,wherein the shield is colorless after being sterilized using gammaradiation.
 14. A flexible optical web comprising: a substrate having asubstrate refractive index; a first coating layer applied to thesubstrate, the first coating layer having a first coating refractiveindex, a second coating layer applied to the first coating layer so thatthe first coating layer is positioned between the substrate and thesecond coating layer, the second coating layer having a second coatingrefractive index, a third coating layer applied to the second coatinglayer so that the second coating layer is positioned between the firstcoating layer and the third coating layer, the third coating layerhaving a third coating refractive index, wherein the first coatingrefractive index is greater than the second coating refractive index andthe second coating refractive index is greater than the third coatingrefractive index, and wherein the substrate refractive index is greaterthan the first coating refractive index.
 15. The optical web of claim14, further comprising a posterior coating layer applied to thesubstrate, the posterior coating layer having a posterior coatingrefractive index, wherein the posterior coating refractive index is lessthan the substrate refractive index.
 16. The optical web of claim 14,wherein the substrate refractive index is at least about 1.53, whereinthe first coating refractive index is between about 1.44 and about 1.48,and wherein the second coating refractive index is no greater than about1.43.
 17. The optical web of claim 14, wherein the optical web isfurther coated with at least one of a scratch resistant coating, ananti-fog coating, an anti-fingerprint coating, a matte coating, a hardcoating, or an anti-glare coating.
 18. An optical web comprising: asubstrate having a substrate refractive index of about 1.64 to about1.67, the substrate having an anterior side and an opposing posteriorside; an anterior coating including a plurality of coating layers,individual coating layers having individual refractive indexes, whereinthe individual refractive index of an individual coating layer formingthe anterior side of the optical web is about 1.33 to about 1.42, aposterior coating including a first posterior layer applied to theposterior side of the substrate, the first posterior layer having afirst posterior layer refractive index, wherein the substrate refractiveindex is greater than the first anterior refractive index and the firstposterior refractive index.
 19. A method of manufacturing an opticalstructure comprising: applying an anterior coating to an anterior sideof a substrate; and applying a posterior coating to a posterior side ofa substrate, wherein the substrate has a substrate refractive index ofabout 1.64 to about 1.67, wherein the anterior coating includes a firstanterior layer applied to the anterior side of the substrate, the firstanterior layer having a first anterior layer refractive index and anindividual refractive index of an individual anterior layer forming theanterior coating of the optical web is about 1.33 to about 1.42, whereinthe posterior coating includes a first posterior layer applied to theposterior side of the substrate, the first posterior layer having afirst posterior layer refractive index, wherein the substrate refractiveindex, the first anterior layer refractive index, and the firstposterior layer refractive index are greater than 1.00, and wherein thesubstrate refractive index is greater than the first anterior refractiveindex and the first posterior refractive index.
 20. The method of claim19, further comprising cutting the laminated sheet to form an opticalshield, and attaching the optical shield to a garment.
 21. The method ofclaim 20, wherein the optical shield is sterilized using gammaradiation, and remains colorless after sterilization.
 22. The method ofclaim 19, further comprising laminating at least two optical structurestogether via an adhesive layer, wherein the adhesive layer is configuredto allow one optical structure to be peelably removed from the other,wherein the adhesive layer has an adhesive refractive index matched towithin about 0.2 of the substrate refractive index.